Types of the OED include an organic light emitting device (OLED), an organic photovoltaic cell, an organic photo conductor (OPC), or an organic transistor. For example, a conventional OED sequentially includes a glass substrate, a transparent electrode layer, an organic layer including an emitting unit, and a reflective electrode layer.
In a structure called as a bottom emitting device, the transparent electrode layer may be formed as a transparent electrode layer, and the reflective electrode layer may be formed as a reflective electrode layer. In addition, in a structure called as a top emitting device, the transparent electrode layer may be formed as a reflective electrode layer, and the reflective electrode layer may be formed as a transparent electrode layer. From the electrode layer, electrons and holes are injected, and recombined in an emitting unit, thereby generating light. The light may be emitted to the substrate in the bottom emitting device, and emitted to the reflective electrode layer in the top emitting device.
In the light emitted from the organic layer, a part of the light incident at an interface of each layer at a critical angle or more is not emitted and trapped because of total internal reflection, thereby emitting only a very small amount of the light. Accordingly, for example, as disclosed in the patent document 1, there is an attempt to increase light extraction efficiency. However, light extraction technology known so far generally uses a rigid substrate such as a glass substrate, and thus is not effectively applied to a device using a flexible substrate having a different property from the glass substrate.